Conventionally, a method of contacting a conductive surface of a web or a metal web to a cathode roller, arranging a plating bath in which an anode is immersed in a plating solution is arranged on the front or the back, and forming a plate film in the plating bath is known as a method of continuously forming a plate film on the web while running the web such as a plastic film. If the plate film is continuously formed on the web through such method, a plate film of a desired thickness, which is easily thickened on the web, can be formed by repeatedly passing a unit arranged with a cathode-anode (see patent document 1).
In recent years, a wiring substrate of a mode in which a web of polyimide film or polyester film and a copper foil are combined is given attention for a flexible circuit substrate used in electronic devices, electronic parts, semiconductor packages, and the like. Such substrate includes a substrate normally called a “three-layer type” in which a copper foil is laminated to the web by way of an adhesive, and a flexible circuit substrate normally called a “two-layer type” in which the metal film is formed through plating and the like on the web without interposing an adhesive. The latter two-layer type is given more attention with advancement in miniaturization of the wiring pitch of the circuit.
The current situation related to such flexible circuit substrates is as follows. The three-layer type print circuit substrate uses epoxy resin or acryl resin for the adhesive, and thus has a drawback in that the electrical characteristic degrades by the impurity ion contained in the resin. Furthermore, since the heat resistance temperature of the adhesive is between 100° C. and 150° C., such high heat resistance (higher than or equal to 300° C.) cannot be sufficiently exhibited even if polyimide is used for the base film material, whereby spec down of the heating temperature inevitably occurs in wire bonding etc. to the IC chip requiring high temperature mounting. Moreover, since the general film thickness of the copper film is 18 μm or 35 μm in the three-layer type print circuit substrate, the copper is too thick and the etching rate significantly lowers when performing patterning at smaller than or equal to a pitch of 80 μm (copper wiring 40 μm, gap 40 μm), whereby the circuit width on the surface side of the copper film and the circuit width on the adhesive surface side differs significantly or significant thinning occurs as a whole by etching and the target circuit pattern may not be obtained.
In recent years, in order to solve the problems of the three-layer type, the substrate normally called the “two-layer type” obtained by electrolyte copper plating after depositing various types of metals deposited on the web surface through various depositions methods such as PVD method including vacuum deposition method, sputtering method or various ion plating method, so-called CVD method of vaporizing and depositing chemicals containing metal, and the like without interposing an adhesive, or after plating various types of metals through an electroless plating method is proposed. The two-layer substrate has characteristics in that the copper film thickness can be freely changed through the electrolyte copper plating such as the circuit pattern having a pitch of 40 μm can be easily formed if the copper film thickness is 8 μm, and in that the heat resistance temperature of various types of webs can be reflected as it is.
From the above situations, demands on the film with a plated coating film are increasing. However, since the web is run while contacting the conductive surface to the cathode roller in the conventional method, scratches and burr-like protrusions involved therewith sometimes are produced at the very delicate conductive surface of the web. Furthermore, since the cathode roller is contacted to the entire width of the web, the entire length of the cathode roller becomes long by an amount the width of the web is increased, whereby the roll diameter inevitably becomes large to maintain strength and the size of the power supply device itself becomes large.
In recent years, the miniaturization of the circuit pattern is advancing, and the surface quality required on the plate film is also becoming stricter therewith. Thus, a development of a process that does not produce microscopic scratches and protrusions is being dedicatedly carried out.
Patent document 2 proposes a plating process called a clip method in which the end of the web is sandwiched and pinched with a power supply clip, and the web is passed through the plating solution in such state to perform plating on the web, where microscopic scratches and the like do not produce in the product as only the end of the web, which is not manufactured, is gripped, and a satisfactory surface quality can be obtained. However, a large conveyance system for running the power supply clip, a large additional facility for deplating step of removing the plate film precipitated on the power supply clip, and the like are required. The foreign substances floating in the plating solution become the cause of plating defects called zara and thus high cleanliness is required for the plating solution, but the plating solution tends to be easily polluted by foreign substances such as abrasion powder since various movable parts are arranged on the upper part of the plating solution. Furthermore, plating is not performed on the portion to be gripped with the power supply clip and the resistance value becomes large at the relevant portion since the film thickness of the electrically conductive film becomes thin only at the relevant portion, whereby problems such as change in color and alteration arise at the periphery by the Joule heat when large current is flowed.
Patent document 3 proposes a method of supplying power while pressing a plate spring-shaped power supply electrode to the end of the web and performing plating on the web, where satisfactory surface quality with fewer scratches etc. is similarly obtained in the product according to such method. However, the plating solution and the peripheral devices are polluted by the abrasion powder at the same time as the abrasion of the electrode since the power supply electrode is constantly in a rubbing state. Since a brake is constantly applied by the electrode, an uneven tensile distribution produces in the width direction of the web, which is a large problem from the standpoint of stable running.
Patent document 4 illustrates a general vertical plating device using a roll-shaped power supply electrode, and proposes a so-called dumbbell-shaped power supply electrode in which the outer diameter of the roller at the central part is reduced so that only the ends contact the web as one type of a cathode roller shape. According to such method, a product with lesser surface defects such as scratches at the central part of the web where the roller does not contact can be manufactured. However, since the angular speed of the roller is the same at both ends, a peripheral speed difference creates at both ends if the outer diameter of both ends contacting the web does not match even by a small amount, and thus an extremely high processing accuracy is required. If the outer diameter does not match by any possibility, the abrasion of the electrode and production of tensile distribution in the width direction occur as one of the ends contact while sliding.
Patent document 5 proposes a method of supplying power by exposing only the upper end of the web from the plating bath and closely attaching the belt-shaped electrode to the exposed portion without contacting the central part of the web to perform plating without affecting characteristics such as bulkiness of nonwoven cloth. According to such method a swell, a high quality plate film without scratches and dents at the central part is obtained. However, according to such method, the film thickness is very thin as the upper end of the web is constantly not plated, and change in color and alteration of the film occur by Joule heat when large current is flowed due to the large resistance. In the web of plastic film and the like having poor elasticity in the thickness direction, even if the web and the belt-shaped electrode are sandwiched with the guide roller and closely attached with the nip force, the contact resistance of the electrode and the web at other than the nipped location becomes large as close attachment force only generates at the guide roller portion. Thus, problems by heat arise when large current is flowed.
Patent document 6 proposes a conveyance method of pressing a rotating body of small width on a conveyance roller, where the rotating body also acts as a power supply electrode. A product with fewer scratches at the surface opposite to the surface wrapped to the conveyance roller can be manufactured by installing the rotating body at the end of the web as a power supply electrode using such method. However, according to the knowledge of the inventors of the present invention, a roller of hard material needs to be used as folding wrinkles produce at the web with the edge of the electrode if a soft material is used for the material of the conveyance roller in such method, and thus problems of scratches may not be resolved at the surface wrapped to the conveyance roller.    Patent document 1: Japanese Unexamined Patent Publication No. 7-22473    Patent document 2: Japanese Patent Publication No. 2005-507463    Patent document 3: Japanese Unexamined Patent Publication No. 2005-248269    Patent document 4: Japanese Unexamined Patent Publication No. 2003-321796    Patent document 5: Japanese Unexamined Patent Publication No. 8-209383    Patent document 6: Japanese Unexamined Patent Publication No. 2004-263215